This invention relates generally to apparatus for coupling a member implanted in a body with a member located outside the body. More particularly, but not by way of limitation, the invention relates to a bio-electronic signal coupling device (such as a hearing aid having a cochlear implant unit and a sound receiving unit) utilizing rare-earth magnets to properly align and secure an external member (such as the sound receiving unit) with an internal member (such as the cochlear implant unit).
In the medical implantable electronic prosthesis field it is necessary to maintain proper alignment between units implanted within the body and units associated therewith but located externally of the body. Specifically, in medical prostheses involving electrical signal transfers, such as hearing aids, it is critical to maintain a proper alignment between the implanted and external units to insure effective signal transfer.
For example, a hearing aid known as an auditory neural prosthesis is used to electrically stimulate a user's auditory nerve directly or within the cochlea thereby to enable recognition of environmental sounds and to improve lip-reading skills. Such a prosthesis includes an internal, subcutaneously located signal receiving unit implanted in the user so that an electrical signal can be conducted to a cochlea of the user. The prosthesis also includes an external sound detecting and transmitting unit located outside the skin of the user.
For the sound detecting and transmitting unit to effectively transmit to the receiving unit electrical signals corresponding to the detected sounds, the sound detecting and transmitting unit must be maintained in proper alignment with the receiving unit. Presently proposed or used devices attempt to maintain alignment by utilizing eyeglass frames specially constructed to carry the sound detecting and transmitting unit. This frame structure has the shortcoming of permitting misalignment between the external and internal units because the eyeglass frames can slip and otherwise become easily moved. Such misalignment decreases, if not totally eliminates, the amplitude of the coupled signal received by the receiving unit. This decrease or loss of signal results in decreased or lost cochlea stimulation which causes frustration in the user of the apparatus because he or she has to continually readjust the eyeglass frames to maintain the apparatus operative. This misalignment also hampers the training, evaluation and use of the prosthesis user.
If the eyeglass frame structure were used with multichannel auditory neural prostheses which are being developed to provide frequency coding of detected sounds, the reliability of such multi-channel devices would be greatly decreased because accurate alignment is critical to insure that each of the plurality of signals transmitted by the transmitter means in the multi-channel transmitter unit is received by the proper receiver means in the implanted multi-channel receiving unit.
Although proper alignment must be maintained in medical apparatus having units located both beneath the surface of the skin and above the skin, it is desirable that there be no mechanical connection which extends through the skin of the user between the internal and external units. Although no mechanical connection, which could rigidly maintain a predetermined distance between the internal and external units so that no compression of the intervening skin occurred, is wanted, neither is there desired a coupling device which adversely affects, such as by compression, the skin extending between the implanted unit and the external unit. Therefore, what is desired is an apparatus which secures the external unit with the internal unit without adversely affecting the intervening tissue.
Although there have been proposed and made medical apparatus having implantable units and external units which need to be coupled or held in alignment by some means, such as the aforementioned type of hearing aid using an eyeglass frame, we do not know of any such apparatus which discloses or suggests our invention as disclosed and claimed hereinbelow.